Tire pressure gauge



Dec. 1. I95? 0. F. FLETCHER 2,66UT890 TIRE PRESSURE GAUGE Filed July 17,1950 Ihmentor ORION E FLETCHER (Ittornegs Patented Dec. 1, 1953 UNITEDSTATES i ATENT OFFICE 2 Claims.

This invention relates to pressure gages, and more particularly to gagesfor measuring pressure of pneumatic tires.

One of the objects of the invention is to provide a tire gage of theliquid column type wherein the pressure graduations betweenpredetermined pressure limits may be spread more evenly throughout thelength of the gage.

Another object is to render the gage. more compact.

Another object is to provide a gage in which the calibrations forpressure difference increments' are more uniformly spaced along itslength.

Another object is to provide a bleed device to prevent surging andbreaking of the liquid column.

Another object is to provide a gage with an extensible defiator devicefor rendering the gage more readily attachable to relativelyinaccessible tir valves.

Further objects are to provide a gage which is simple in construction,readily and economically fabricatable, and highly accurate in operation.

Still further objects, advantages, and salient features will become moreapparent from the description to follow, the appended claims, and theaccompanying drawing, in which:

Figure 1 is a side elevation of one form of the invention;

Figure 2 is a section taken on line 2-2, Figure 1, portions being shownin side elevation;

Figure 2A is an enlarged section taken on line 2-2, Figure 1, a portionbeing broken out;

Figure 3 is a longitudinal section of an alternative form of deflatorwhich may be employed with any form of the invention disclosed; and

Figure 4 is an alternative form of liquid column tube which may beemployed with any form of the invention.

Referring in detail to the drawing, and particularly Figures 1, 2 and2A, the gage i comprises, in general, a transparent tube II having asmall bore I2 extending longitudinally thereof, a chamber I3 containinga liquid I4, an expansible tubular diaphragm I5 disposed within theliquid chamber, a defiator and check valve assembly I 6, and an airpressure release valve device ll.

Tube II may be'of any suitable transparent material, such as thesynthetic plastics now in common use. The tube is provided with anenlarged air chamber I8 communicating with the upper end of bore I2, thechamber being closed at its upper end by a cap Iii cemented or otherwiseafiixed to tube I I and a body of self-sealing rubber 2i! interposedbetween the cap and upper end of the air chamber. The lower end of thebore communicates with liquid chamber I3 which is provided with afrusto-conical air chamber 2i which a nail of a finger, such as disposedbetween the lower end of bore I2 and the upper level 22 of the liquid Il.

Diaphragm I5 is formed as a tubular sack of rubber, plastic, or otherresilient material and is disposed within reservoir I3, its lower endbeing provided with a circular flange 23, one side of which abuts thelower edge of the tube II, the other side abutting a disk 24, the latterhaving a small bleed port 25 therein.

A sleeve 26 surrounds tube I I in sealing engagement therewith and isprovided with an annular abutment 2! which abuts the lower surface ofthe disk. When the parts are assembled leakage of liquid or air aroundthe edge of flange 23 is preeluded.

To permit air from a pneumatic tire to enter air chambers 28, 29 adefiator I6 is provided, this device comprising a cup-shaped member 39adapted to surround the end of a tire valve stem and havin a projection3| which engages the tire valve core and opens it. A rubber seal ring 32engages the end of the tire valve stem and prevents leakage, the airpassing through one or more holes 33, through a felt filter pad 34,through bore 35, around check valve disk 36 and thence into chambers 23,:29. The check valve just referred to may be a fiat disk of rubber-likematerial or any other suitable type of check valve. The disk shown isretained from excessive movement away from its seat by a snap ring 35'.A pocket clip 31, similar to those employed on fountain pens, is securedto the device by an integral ring member 38 on the clip disposed betweenthe lower end of sleeve 25 and cup member 30.

To permit release, of air pressure in chambers 28, 29, a release valveI! is employed, this valve comprising a valve stem 39 having a cupmember 40 containiu an annular rubber seal ring M engageable with valveseat 42. A spring 43 urges the seal ring against seat 42 and the valvemay be moved away from its seat by an actuator 44 afllxed to the valvestem, the outer exposed end of the actuator being substantially flushwith sleeve 25 and a groove 45 being provided into the thumbnail, maymove when the valve is opened. When opened, air from chambers 28, 29discharges through clearance space around the actuator. To facilitatefabrication of the valve seat, assembly of the parts, and to form aguide for valve stem 33, a plug it is provided in sleeve 26, this beingcemented or otherwise secured to prevent air leakage.

In Figure 3 is illustrated an alternative form of defiator which may beemployed with tire valves which are relatively inaccessible, such as ondual tire trucks, etc. In this construction the lower end of sleeve 26ais provided with a removable sleeve which contains a coil of resilienttubing 5|, one end of which is connected This tubing may be of anyresilient material,

such as certain plastics, which will automatically resume their nestedposition in tubingil when sleeve 53 is replaced on sleeve 28a.

In the operation of the invention sofar described, the oleflator isappliedtto: thetireivatlve stem, air enters chamber 28, passes through.bleed port 25 and intochamber 29 expanding tubular diaphragm l forcingthe liquid into bore l2, and compressing air therea-bove, the pressurebeing read on graduations 52. The purpose of providing air chamber 2! isto-shorten the overall length of the gage, since by having a chamber ofl'argercross section than the bore l2, and hence a greater volume perunit length thereof, the lowest desiredgraduation, such as say twentypounds per square inch, may be disposed near the lower end of bore 12.If this enlarged air chamber were not provided it is apparent that theliquid would be forced a considerable distance along bore l2 to read asimilar pressure, thus requiring a longer tube. Air chamber 18 is alsoadvantageous since it spreads a range of pressures such as betweentwenty and forty pounds, as shown in'Figure 1, over a longer distance,thus making. the gage more sensitive and easier to read accurately, thisbeing due to the greater quantity of air which is compressed above theliquid column. It will be apparent that if chamber 18 were omitted,other proportions being the same, the forty pound graduation would becloser to the twenty pound graduation, and hence the spread betweengraduations per unit length of' the bore would: be less.

The graduations per unit difference in pres:- sure are, of course, notequal, which has been illustrated in Figure 1, the graduations becomingcloser together toward the upper end of the bore. To render them moreequal, the construction shown in Figure 4. may be employed wherein borelZa, is tapered, being larger at the bottom than at the top. With thisconstruction, by proper choice of cross sectional taper the calibrationsmay be disposed equal or substantially equal distances apart, as shownat 52c, Figure 4.

It will be apparent that after the. deflator has been applied to thetire valve stem the pressure in chambers 28, 29 will be the same as. inthe tire. When the deflator is removed from the valve stem, check valve36 will close and thus trap air in such chambers and the gage mayberemoved and read at, leisure. When it is. desired to return the liquidto its. normal position actuator 44 is depressed, thus reducing thepressure in chambers 28, 29. to atmospheric pressure. The purpose ofbleed port is to permit air to enter chamber 29 slowly, thus obviatingsurging of the liquid column. in bore l2. Also, it, permits the air tobe exhausted slowly permitting the liquid column to descend graduallyand without breaking of the column and necessitating jarring or shakingit down in the bore in a manner similar to the operation required inclinical thermometers.

While the gage may be calibrated in any manner, it is preferred tocalibrate it with a slight pressure in the bore to slightly collapsediaphragm I5. To attain this, liquid I4 is added to reservoir I3 andinto bore l2 above the lowermost graduation, that is, above the twentypound graduation. Cap I9 is then applied and sealed to tube 10. Ahypodermicneedleis then. inserted through bore 53 and seat 2'3 and thedeflator applied to a source of pressure which is exactly twenty poundsper square inch. Air is forced into bore I2 with the needle until theliquid is depressed to the twenty pound mark, after which the needle is.removed, the self-sealing material Zilsealing the needle hole therein asit is withdrawn; Bore 53. isthen permanently closed with a suitableplug. When the pressure is released the liquid level falls to .aposition in chamber 2| and the diaphragm IE will be partially collapsed.

Any suitable liquid may be employed; however, ethylene glycol-has theadvantage that it will withstand low temperatures without freezingandhas been found to give satisfactory results. Any suitable dye may alsobe employed to render the liquid column clearly visible and the tube [6need not be clearly transparent, but only transparent to the'extent thattheliquid column may be clearly visible. Colored material for the tubeis therefore contemplated within the purview of transparent ashereinafter set forth in the claims;

Having described the invention, what I' claim as new is:

1'. A tire gage comprising, an elongated transparent member havingarelatively long bore extending longitudinally thereof, means comprisinga plug-like member of rubber having. self sealing properties closing oneend of the bore, the other end being of enlarged diameter forming aliquid chamber, an elongated tubular diaphragm extending into the liquidchamber, means forming a seal between the end of the tubular member andthe open end of the diaphragm whereby a closed chamber is formed fortheliquid which surrounds the tubular diaphram, whereby when the tubulardiaphragm is expended inresponse to internal pressure some of thesurrounding liquid will be displaced and move into that part of the boreof smaller diameter compressing air therein and increasing the airpressure, whereby the distance that theliquid moves into that portion ofthe bore of smaller diameter will correspond'to the pressure in thetubular diaphragm.

2. A device in accordance with claim 1 in which means is operativelyassociated with the open end of the. tubular diaphragm for effectingacommunication between a chamber containing a fi'uid under pressure andthe interior of the tubular diaphragm.

ORION F-L FLETCHER.

References: Cited in. the. file of this patent- UNITED STATES PATENTSFrance Sept. 18, 1939

